1. Field of the invention
The present invention relates to a magnetic recording medium giving a high S/N ratio.
2. Description of Related Art
Magnetic recording and reproducing equipment has a higher density year by year and a magnetic recording medium having excellent record and reproduction property at a short wave length is required. In order to satisfy this requirement, a thin film magnetic recording medium is developed. The thin film magnetic recording medium is prepared by a vacuum deposition method, a spattering method, a plating method and the like and has an excellent record and reproduction property at a short wave length. Co, Co--Ni, Co--Ni--P, Co--O, Co--Ni--O, Co--Cr, Co--Ni--Cr, Co--Cr--Ta, Co--Cr--Pt and the like are studied for a magnetic layer of the thin film magnetic recording medium.
When the thin film magnetic recording medium is practically used as a magnetic tape, the vacuum deposition method is most suitable for the preparation method. A vacuum deposited tape having a Co--Ni--O magnetic layer positioned on a polymer substrate has been practically used as a Hi-8 type VCR tape.
The magnetic layer in the vacuum deposited tape comprises crystalline grains grown in a direction diagonally inclined to a line normal to the film plane and has an easy magnetization axis inclined to a line normal to the film plane. Namely, the easy magnetization axis is not present in the film plane or in a direction normal to the film plane but is present in a direction diagonally inclined to the normal line and in the normal plane including an incident direction of evaporated atoms to the substrate. In the commercially available vacuum deposited tape for Hi-8 type VCR, the easy magnetization axis inclines at 70.degree. . to the line normal to the film in the normal plane including a longitudinal direction of the tape. The longitudinal direction of the tape means a direction along the length of the tape.
In future, the magnetic recording and reproducing equipment will be required to be miniaturized and have a larger capacity. In order to satisfy this requirement, it is necessary to improve a linear recording density and a track density. Therefore, the magnetic tape is required to have a high S/N ratio, particularly a high S/N ratio in a short wave length range.